Hemiparesis is the most commonmotor impairment after stroke that frequently results in persistent hand dysfunction. The long-term goal is to understand the mechanisms underlying the recovery of hand motor function after stroke to provide a scientific rationale for rehabilitation protocols used in clinical practice. The specific hypothesis is that the non-involved hand can assist in the recoveryof the involved hand. We base this hypothesis on the observation that prior grasping with the non-involved hand improved anticipatory planning of grasp to object weight with the involved hand in some subjects after stroke. Based on these observations, the focus of this proposal is to investigate the type and nature of information relayedacross the hemispheres, by prior manipulation with the non-involved hand, to improve planning and execution of grasp with the involved hand in patients with post-stroke hemiparesis and age-matched controls. The specific aims are to: (1) Investigate whether weight-related information from muscle sensors or tactile information from the fingertips mediates the transfer of anticipatory control to object weight across hands; (2) Examine whether weight-related information for transfer of anticipatory control across hands requires task- specific muscular activity; and (3) Determine whether prior manipulation with the non-involved hand improves the temporal and spatial neuromuscular control of grasping with the involved hand. Psychophysical methods using a grip instrument will be used to examine the type of information necessary for planning of grasp, and quantitative electromyography will be used to investigate the contribution of the non-involved hand in improving neuromuscular control of grasp in the involved hand. This project is proposed as part of a career development plan to obtain training in systemsneuroscience, motor control, andmovement biomechanics, while acquiring skills in psychophysical and electromyographic techniques. The PI is an Instructor in the Department of Rehabilitation Medicine which is strongly committed to supporting research in this field. The Mount Sinai School of Medicine and Teachers College provide a rich environment to enable the PI to become an independent investigator studying the mechanisms of recoveryafter stroke, and to translate research in motor control into therapeutic protocols for the rehabilitation of voluntary motor functions after brain injury.